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Mechanistic investigation on Ce addition in tuning recrystallization behavior and mechanical property of Mg alloy

journal of Materials science & Technology 2023年第1期132卷 1-17页

作者： j.R.li D.s.xie Z.R.Zeng B.song H.B.xie R.s.pei H.C.pan Y.p.Ren G.w.Qin Key laboratory for Anisotropy and Texture of Materials(Ministry of Education) College of Materials Science and EngineeringNortheastern UniversityShenyang110819China College of Engineering and Computer science Australian National UniversityACT 2601Australia school of Materials and Energy Southwest UniversityChongqing 400715China Institute for physical Metallurgy and Materials physics RWTH Aachen UniversityAachen 52062Germany

Constructing bimodal grain structure is a promising approach to achieve the high strength-ductility syn-ergy in Mg *** of bimodal grain is closely related to the dynamic and/or static recrystal-lization process,which has not been fully understood in the typical Mg-RE based *** this work,it is claimed for the first time that the minor Ce addition(∼0.3 wt%)into Mg matrix significantly pro-motes the pyramidaland non-basaldislocations at the early stage of extrusion,which con-sequently enhances the formation of sub-grain boundaries via the movement and recovery of pyramidal II-type*** this stage,fine sub-grain lamellae are widely observed predominantly due to the low migration rate of sub-grain boundary caused by the limited mobility of*** the later stage,the sub-grains continuously transform into dynamic recrystallized(DRXed)grains that have10¯10Taylor axis and also strong fiber texture,indicating substantial activation of pyramidal II-type*** low mobility ofdislocations,accompanied with the solute drag from grain boundary(GB)segregation and pinning from nano-phases,cause a sluggish DRX process and thus a bimodal microstructure with ultra-fined DRXed grains,∼0.51μ*** resultant texture hardening and grain refinement hardening effects,originated from bimodal microstructure,result in a yield strength of∼352 Mpa,which is exceptional in Mg-Ce dilute *** work clarifies the critical role of Ce addition in tuning recrystallization behavior and mechanical property of magnesium,and can also shed light on designing the other high-performance Mg alloys.

关键词： Mg alloys Recrystallization behavior Mechanical property pyramidal dislocation Thermal stability

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难治性肺炎支原体肺炎患儿合并栓塞的危险因素分析及列线图预测模型的构建

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中国当代儿科杂志 2024年第5期26卷 486-492页

作者：谢利娜冯特郭燕军张玉会李远哲张万存郑州大学附属儿童医院儿科呼吸内科河南郑州450018

目的分析难治性肺炎支原体肺炎(refractory Mycoplasma pneumoniae pneumonia,RMpp)患儿合并栓塞的危险因素,并构建列线图预测模型。方法回顾性纳入2019年1月—2023年10月在郑州大学附属儿童医院确诊为RMpp的175例患儿,根据是否合并栓塞... 详细信息

目的分析难治性肺炎支原体肺炎(refractory Mycoplasma pneumoniae pneumonia,RMpp)患儿合并栓塞的危险因素,并构建列线图预测模型。方法回顾性纳入2019年1月—2023年10月在郑州大学附属儿童医院确诊为RMpp的175例患儿,根据是否合并栓塞,分为栓塞组(n=62)和非栓塞组(n=113),采用多因素logistic回归分析筛选RMpp患儿合并栓塞的危险因素,并应用R软件构建列线图预测模型。结果多因素logistic回归分析显示,高D-二聚体、高白细胞介素-6、高中性粒细胞与淋巴细胞比值、肺坏死、胸腔积液是RMpp合并栓塞的危险因素(ppsmer-lemeshow拟合优度检验结果表明,该模型与实际情况拟合较好(ppp合并栓塞的危险因素,根据上述危险因素构建列线图模型用于预测RMpp合并栓塞具有较高的临床价值。

关键词：难治性肺炎支原体肺炎列线图预测模型危险因素儿童

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肿瘤患者跌倒风险感知量表的编制及信效度检验

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护理学杂志 2024年第4期39卷 6-10页

作者：罗瑞君万永慧解荣李颖陈文林武汉大学人民医院光谷院区肿瘤科湖北武汉430223 武汉大学人民医院肿瘤中心湖北武汉430223

目的编制肿瘤患者跌倒风险感知量表并检验信效度,为肿瘤患者跌倒防范提供自评工具。方法通过文献回顾、专家函询、小组讨论等方式构建量表,选取407例肿瘤患者进行调查,检验量表信效度。结果肿瘤患者跌倒风险感知量表包括跌倒认知易感知... 详细信息

目的编制肿瘤患者跌倒风险感知量表并检验信效度,为肿瘤患者跌倒防范提供自评工具。方法通过文献回顾、专家函询、小组讨论等方式构建量表,选取407例肿瘤患者进行调查,检验量表信效度。结果肿瘤患者跌倒风险感知量表包括跌倒认知易感知性(5个条目)、生理状况易感知性(12个条目)、个人活动易感知性(5个条目)、环境因素易感知性(5个条目)、跌倒严重性感知(3个条目)5个维度共30个条目。探索性因子分析提取5个公因子,累计方差贡献率66.746%。量表总的Cronbach′sα系数为0.926,折半信度为0.672,各维度Cronbach′sα系数为0.914~0.970,折半信度为0.877~0.963。量表水平的内容效度指数为0.867,条目水平的内容效度指数为0.813~1.000。验证性因子分析结果显示,χ^(2)/df=1.845,RMsEA=0.059,GFI=0.840,CFI=0.971,NFI=0.939,AGFI=0.811,模型适配良好;AVE平方根均显著大于相关系数,各维度之间有显著相关性(均p<0.05)。结论肿瘤患者跌倒风险感知量表信效度良好,可用于肿瘤患者跌倒风险感知的评估。

关键词：肿瘤跌倒跌倒预防风险感知评估量表信度效度

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Dynamic buckling mechanism of pillar rockbursts induced by stress waves

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journal of Rock Mechanics and Geotechnical Engineering 2019年第5期11卷 944-953页

作者： j.Deng N.s.Kanwar M.D.pandey w.-C.xie Department of Civil Engineering Lakehead UniversityThunder BayOntarioP7B 5E1Canada Centre of Excellence for sustainable Mining and Exploration Lakehead UniversityThunder BayOntarioP7B 5E1Canada Department of Civil and Environmental Engineering University of WaterlooWaterlooOntarioN2L 3G1Canada

Rockbursts are sudden and violent rock failures that can lead to huge production and equipment losses,injury or death of mining *** has been regarded as one of the key mechanisms of rockbursts,which are often induced by dynamic loads from mining excavations,such as drilling and blasting in underground *** paper attempts to investigate the dynamic buckling mechanism of pillar rockbursts in underground mining,by considering rockbursts as a dynamic stability problem of underground rock *** results include:(1)A new explanation of the“sudden and violent”phenomenon of rockbursts,characterized by exponential growth of the amplitudes of transverse displacement responses,even in the presence of rock damping;(2)Identification of the critical role in inducing rockbursts of dynamic loads that bear frequencies approximately double the natural pillar frequency;(3)The greater influence on rockburst occurrence of the amplitude of dynamic component relative to the static component of loads;and(4)Quantification of the relative effects of stress waveform of dynamic loads on pillar rockbursts,which are in decreasing order if other parameters remain constant:rectangular,sinusoidal,and exponential *** examples are provided and limitations of the approach are *** research is motivated by the on-going and ubiquitous occurrence of rockbursts in underground excavations all around the *** contrast to conventional methods that use rock specimens or rock materials to study rockbursts,this investigation emphasizes the structural effects on rockbursts,which has potential applications in hard rock mining engineering.

关键词： pillar rockbursts Buckling mechanism stress waves structural rock mechanics

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The effects of fabrication atmosphere condition on the microstructural and mechanical properties of laser direct manufactured stainless steel 17-4 pH

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journal of Materials science & Technology 2019年第7期35卷 1315-1322页

作者： D.wang C.T.Chi w.Q.wang Y.l.li M.s.wang X.G.Chen Z.H.Chen X.p.Cheng Y.j.xie Institute of Applied physics Jiangxi Academy of SciencesNanchang 330029China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China school of Mechanical and Electrical Engineering Nanchang UniversityNanchang 330029China jiangxi Reman Additive Technology Co. ltd Nanchang 330096China

The effects of atmosphere conditions on microstructural and mechanical properties of stainless steel 17-4pH components fabricated by laser direct manufacturing (lDM) were investigated through mea-surements on phase constitution, porosity, tensile strength, fracture morphology, hardness and evolution of substrate temperature. Results showed that the samples produced in air atmosphere condition pos-sessed higher tensile strength and hardness for both as-deposited and heat-treated states than that in Ar chamber condition, due to dispersion strengthening effect of amorphous oxide particles and nitrogen solution strengthening as a result of higher content of oxygen and nitrogen. The temperature of substrate heat accumulation was higher in Ar chamber condition, leading to dramatically lower porosity and more reverse austenite, which also contributed to the lower strength and hardness.

关键词： Additive manufacturing laser direct manufacturing 17-4 pH stainless steel Fabrication atmosphere Mechanical properties

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limit of crustal drilling depth

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journal of Rock Mechanics and Geotechnical Engineering 2017年第5期9卷 989-992页

作者： Y.s.Zhao Z.j.Feng B.p.Xi D.Yang w.G.liang Z.j.w.n Key laboratory of In situ property-improving Mining of Ministry of Education Taiyuan University of Technology College of Mining Engineering China University of Mining and Technology

Deep drilling is becoming the direct and the most efficient means in exploiting deep mineral resources,facilitating to understanding the earthquake mechanism and performing other scientific researches on the Earth’s *** order to understand the limit of drilling depth in the Earth’s crust,we first conducted tests on granite samples with respect to the borehole deformation and stability under high temperature and high pressure using the triaxial servo-controlled rock testing *** the critical temperaturepressure coupling conditions that result in borehole instability are ***,based on the testing results obtained and the requirements for the threshold values of borehole deformations during deep drilling,the limit of drilling depth in the Earth’s crust is formulated with ground temperature.

关键词： Drilling well limit of drilling depth High temperature High pressure Borehole instability

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pHAsE TRANsFORMATION AND CHARACTERIsTICs IN FRECKlE AREAs FOR INCONEl 625 sUpERAllOY

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Acta Metallurgica sinica(English letters) 2005年第1期18卷 47-54页

作者： j.X.Dong M.C.Zhang Y.p.Zeng X.s.xie UniversityofscienceandTechnologyBeijing Beijing100083China

The freckle formation and their phase characterizatics in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in an Inconel 625 allay. These results show that in freckle areas a large number of M6C, MC, laves and δ phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and Nb during solidification, which results in almost of these freckle areas covered by these complex precipitated phases and induces small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give a reasonable interpretation of the freckle feature for this alloy.

关键词： freckle superalloy Inconel 625 thermodynamic calculation

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CREEp CRACK GROwTH BEHAVIOR OF AllOY 718 DURING HIGH TEMpERATURE EXpOsURE

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Acta Metallurgica sinica(English letters) 2005年第2期18卷 164-172页

作者： j.X.Dong M.C.Zhang Y.p.Zeng X.s.xie DepartmentofMaterialscience UniversityofScienceandTechnologyBeijingBeijing100083China

Alloy 718 is a precipitation strengthened nickel-based superalloy based on the precipitation of γ″-Ni3Nb (DO22 structure) and γ′-Ni3(Al,Ti) (l12 structure) phases. Creep crack growth rate (CCGR) was investigated after high temperature exposure at 593, 650 and 677℃ for 2000h in Alloy 718. In addition to the coalescence of γ′/ γ″ and the amount increasing of δ phase, the existence of a bcc chromium enriched α-Cr phase was observed by sEM, and the weight fraction of α-Cr and other phases were determined by chemical phase analysis methods. The CCGR behavior and regulation have been analyzed by means of strength and structure analysis approaches. The experimental results show higher the exposure temperature and longer the exposure time, lower the CCGR. This is probably attributed to the interaction of material softening and brittling due to complex structure changes during high temperature exposure. Therefore, despite α-Cr phase formation and amount enhancement were run in this test range. It seems to us a small amount of α-Cr will be not harmful for creep crack propagation resistance, which is critical for disk application in aircraft and land-based gas turbine.

关键词： Alloy 718 creep crack growth rate α-Cr phase

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核桃楸木材的自由干缩特性

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东北林业大学学报 2024年第6期52卷 114-118页

作者：刘泫江谢婧娥唐斌万川杨琳刘洪海南京林业大学南京210037 玛格家居股份有限公司

木材在干燥过程中因失水而导致干缩,非均匀干缩会产生应力限制木材的自由干缩。以核桃楸为试验对象,研究了5 mm厚(纤维方向)分层试件和未分层(整体)试片的自由干缩特性,并对比研究了受限干燥后木材的分层自由干缩特性。研究结果表明:室... 详细信息

木材在干燥过程中因失水而导致干缩,非均匀干缩会产生应力限制木材的自由干缩。以核桃楸为试验对象,研究了5 mm厚(纤维方向)分层试件和未分层(整体)试片的自由干缩特性,并对比研究了受限干燥后木材的分层自由干缩特性。研究结果表明:室温下各层自由干缩系数和绝干干缩率存在显著差异,总体呈现表层向芯层递减的趋势,第1层自由干缩系数(0.254)最大,第7层自由干缩系数(0.165)最小。树皮侧木材的自由干缩系数大于髓心侧。整体自由干缩试件常温干燥过程存在由含水率梯度引起的应力,限制其自由干缩,其弦向干缩率比分层自由干缩试件小0.50%。泡水和汽蒸无法使受限干缩木材的塑性变形完全恢复,利用这种方法测量木材的自由干缩应变不准确。室温下弦向各层自由干缩的干缩率-含水率回归方程的决定系数(R^(2))均高于0.96,利用该方程可以准确计算各含水率点的木材自由干缩应变。

关键词：核桃楸自由干缩含水率应力应变

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REMAINING lIFE AssEssMENT OF A 1Cr5Mo sTEEl BY UsING Z-pARAMETER METHOD

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Acta Metallurgica sinica(English letters) 2004年第4期17卷 601-605页

作者： j.Zhao s.Q.Han s.M.xie H.B.Gao l.wang Department of Materials Engineering Dalian University of Technology Dalian 116024 ChinaDepartment of Materials Engineering Dalian University of Technology Dalian 116024 ChinaDepartment of Materials Engineering Dalian University of Technology Dalian 116024 ChinaDepartment of Materials Engineering Dalian University of Technology Dalian 116024 ChinaDepartment of Materials Engineering Dalian University of Technology Dalian 116024 China

Z-parameter method based on the larson-Miller relationship is proposed to assess remaining life of a 1Cr5Mo steel. The non-linear master curve of stress a vs. larson-Miller parameter p of the steel can be expressed as: p=29.608-5. 085logσ. A family of curves parallel to the master curve can be expressed as: p=29.608-Z-5.085logσ, where the value of Z represents the magnitude deviated from the master curve. A relationship between the value of Z-parameter and the level of spheroidization E (mi-crostructural degradation) can be expressed as: Z=0.203(E-1).

关键词： life assessment spheroidization carbides creep rupture

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